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Ridge-and-Valley Appalachians
]] The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending from southeastern New York through northwestern New Jersey, westward into Pennsylvania and southward into Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia and Alabama. They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province (the Allegheny and Cumberland Plateaus). They are characterized by long, even ridges, with long, continuous valleys in between. The ridge and valley system presents an important obstacle to east-west land travel even with today's technology. It was a nearly insurmountable barrier to railroads crossing the range as well as to walking or horse-riding migrants traveling west to settle the Ohio Country, Northwest Territory and Oregon Country, before the days of motorized transportation. In the era when animal power dominated transportation there was no safe way to cross east-west in the middle of the range; crossing was only possible nearer its extremes except for a few rough passages opened mid-range during the colonial era such as Braddock's Road and Forbes Road, later improved into America's first National Roads (respectively Cumberland Road, Lincoln Highway or designated U.S. 40 and U.S. 30 in later years). Geography The eastern head of the Ridge and Valley region is marked by the Great Appalachian Valley, which lies just west of the Blue Ridge. The western side of the Ridge and Valley region is marked by steep escarpments such as the Allegheny Front, the Cumberland Mountains, and Walden Ridge. Geology These curious formations are the remnants of an ancient fold-and-thrust belt, west of the mountain core that formed in the Alleghenian orogeny (Stanley, 421-2). Here, strata have been folded westward, and forced over massive thrust faults; there is little metamorphism, and no igneous intrusion.(Stanley, 421-2) The ridges represent the edges of the erosion-resistant strata, and the valleys portray the absence of the more erodible strata. Smaller streams have developed their valleys following the lines of the more easily eroded strata. But a few major rivers, such as the Delaware River, the Susquehanna River, the New River, and the Potomac River, are evidently older than the present mountains, having cut water gaps that are perpendicular to hard strata ridges. The evidence points to a wearing down of the entire region (the original mountains) to a low level with little relief, so that major rivers were flowing in unconsolidated sediments that were unaffected by the underlying rock structure. Then the region was uplifted slowly enough that the rivers were able to maintain their course, cutting through the ridges as they developed. Valleys may be synclinal valleys or anticlinal valleys. These mountains are at their highest development in central Pennsylvania, a phenomenon termed the Pennsylvania climax. Significant ridges (from north to south) Photo gallery Image:WV plateau.jpg|Shaded relief map of Cumberland Plateau and Ridge and Valley Appalachians on the Virginia/West Virginia border Image:Ridgecountry.jpg|Pennsylvania's ridge country from Clarks Knob Image:Massanutten-air.jpg|Oblique air photo of Massanutten Mountain, looking southwest. The south fork of the Shenandoah River is visible to the left, as well as a part of the Blue Ridge Mountains. Image:Bedford-co-air.jpg|Oblique air photo facing north of central Bedford County, Pennsylvania, in December 2006, showing Wills, Evitts, and Tussey Mountains from center to right. See also * Geology of the Appalachians * Allegheny Front * Eastern Continental Divide * Tennessee Valley Divide References * Stanley, Steven M. ''Earth System History. New York: W.H. Freeman and Company, 1999. }} Category:Subranges of the Appalachian Mountains Category:Ridges of the United States Category:Valleys of the United States Category:Eastern United States Category:Geography of Appalachia Category:Ridges of Alabama Category:Ridges of Georgia (U.S. state) Category:Ridges of Kentucky Category:Ridges of Maryland Category:Ridges of New Jersey Category:Ridges of New York (state) Category:Ridges of Pennsylvania Category:Ridges of Tennessee Category:Ridges of Virginia Category:Ridges of West Virginia Category:Regions of Alabama Category:Regions of Georgia (U.S. state) Category:Regions of Kentucky Category:Regions of New York (state) Category:Regions of Ohio Category:Regions of Maryland Category:Regions of New Jersey Category:Regions of Pennsylvania Category:Regions of Tennessee Category:Regions of Virginia Category:Regions of West Virginia Category:Physiographic provinces Category:Physiographic regions of the United States